labsvisual / recurse-db

A simple database server for RC pair-programming.

@labsvisual/recurse-db

Introduction

This is the codebase for the pair-programming exercise by RC. This server uses @hapi/hapi as its framework of choice due to its simplicity and agility.

Considering we will not have a lot of time, unit tests cases have been removed giving way only to API (integration) test cases for the endpoints covered (get, set).

Folder Structure

.
├── __tests__
├── bin
├── config
├── lib
│   ├── key-value-store
│   └── shared
└── src
    └── api
        ├── get
        ├── set
        └── stats

__tests__

The __tests__ directory contains the test cases written using the @hapi/lab test framework and the @hapi/code assertion library.

A script has been included in package.json to run all the test cases:

• npm t or npm test

bin

The bin directory contains recurse-db-init shell executable which will be linked by npm to recurse-db on install. To start the server, one must run ./bin/recurse-db-init.

config

This project uses confidence as its configuration provider. During the assignment, we do not need to change any existing config; but we can add more (flush interval, etc.)

This config file makes use of two directives provided by confidence:

• $filter — to do a basic if-else based on certain environment variables; and
• $env — to pull values from the environment.

lib

This directory contains code which is not directly executed; you can imagine this to be a list of internal packages used by this code base.

• router.js — iterates over the src/api directory to find all the controllers and attaches them to the server object;
• loggeer.js — a simple pino instance;
• shared — contains a singleton-initialized instance of the KeyValue store;
• key-value-store — a simple object-based key-value store;

This is the directory where we will do most of our work.

src

This contains execute-on-start code such as the Hapi server instance; the API definitions, etc.

• api — every child-directory becomes an endpoint (get becomes /get/<path>); every child directory MUST contain a routes.js which exports an array of objects containing route definitions, and a controller.js which contains the handler code;
• index.js — contains code to setup the Hapi server.

Prior Art

I did some basic research on how existing KV stores persist data;

• Redis, for example, uses their proprietary file format;
• we can use a similar approach since our state store is basically just a simple JS object;
• probably flush to the file after n changes over m seconds;
• on startup, we can check if this file exists; if so, read it and load otherwise create a new stream.